package/linux-tools: unbreak indentation for perf sub-options

Sub-options of a kconfig symbol are only preperly indented below that
sybol, if there is no inter-mixed sylbols or comments.

In this vase, the comment about perf being unavailable is in-between the
perf symbol and the sub-options, which means the perf options are int
indented.

Move the comment before the definition of perf, so that the options
directly follow the per fsymbol, and so they are properly indented.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>